Drier felt seam securing strip and seam formed therewith



Sept 30, 1947. J. RosLUND l2,428,097

DRIER FELT SEAM SECURING STRIP AND SEMI FORMED THEREWITH Filed Dec. 25,1941 2 Sheets-Sheet 1 Sept. 30, 1947. J. RosLuND 2,428,097

DRIER FELT SEAM SECURING STRIP AND SEM FORMED THEREWITH Filed Dec. 23,1941 sheets-sheet 2 Lm /11 a Patented Sept. 30, 1947 DRIER FELT SEAMSECURING STRIP AND SEAM FORMED THEREWITH John Roslund, Phila delpha,

Pa., assignor to Asten-Hill Mfg. Co., Philadelphia, Pa., a corporationof Delaware Application December Z3, 1941, Serial No. 424,201 6 Claims.(Cl. 154-42) the individual who forms the seam.

It is still another object the cemented have scattered thereith. 'I'heinvention will be understood by reference to the accompanying detaileddescription and the appended drawings.

In such drawings: Fig. 1 is a plan view of a. cement strip for drierfelt seams according to the invention;

Fig. 2 is a corresponding view showing a modification of strip of Fig.1;

from the strip into the fabric;

Fig. 6 is a more or less diagrammatic view ardized length of say twofeet, such as can be easily handled, and to use the required number ofstrips end to end to extend across the full width of the particular feltto be seamed. The strips are sumciently thin so that any excessivelength of the strip may be cut off.

As heretofore mentioned the thickness of the strip is an extremelyimportant factor, since it determines the degree of penetration of thecement of the strip into the opposing fabric portions to be joined. Thethickness of the strip must be carefully controlled to provide anadequate quantity of cement to be absorbed in the pores of the fabricand leave an adequate quantity of cement at the opposing faces of thefabric sections to time the accomplish this, since otherwise the cementis likely to penetrate through to the working surface of the felt,destroying its moisture absorbing capacity completely and tending tocause paper to stick to the felt.

A three ply drier felt having asbestos threads in its surface ply, whichis one of the standard types of drier felt extensively used in papermills, has a thickness varying .between 2 mm. and 3 mm. For such a feltit has been determined that adequate but not an excessive quantity ofcement is obtained by forming the cement strip with a thickness between.5 mm. and 1 mm. It will be found that a strip having a thickness ofapproximately .75 mm. is extremely satisfactory in connection with feltsof the type just referred to and also for felts not including asbestosthreads but having the same general characteristics as to thickness.

It is an essential characteristic of the cement strip that the sameshall be of substantially less thickness than the thickness of theindividual fabric sections to be joined. `Regardless of the thickness ofthe drier felt fabric, it now appears to me that the thickness of thecement strip should not be more than 35% of the thickness of the feltfabric. To provide a sufficient cement content in the strip it also thatthe thickness of the cement strip should not be less than approximately25% of the thickness of the felt fabric in order that a sufficientcement content may be assured to give the necessary strong bond.

It is of course important to use a cement which is waterproof and heatresistant for a drier felt seam, since the drier felt conducts the paperaround heated calendering rolls which drive hot moisture from the paperinto the felt fabric. It is preferred to use a cellulose acetate cementbecause of its ability to satisfy these conditions.

' The cement strip will of course be hard. and may be softened at thetime of formation of the seam through the use of a volatile solvent, orequivalent softening agent which will function at ordinary temperatures.

While the degree of penetration of the cement through the felt may belimited by controlling the thickness of the cement strip, and thus theporosity of the felt for a substantial portion of its thickness adjacentthe working surface maintained, it is obvious that the presence of thecement cuts down the total absorptive capacity of the felt at the seamto the extent that it does penetrate the felt fabric. To offset thiscondition, it is desirable to provide the cement strip with recurrentopenings of appreciable size at frequent intervals. The openings may becircular as indicated at Il in Fig. 1, or may be elongated 7 o together.

5 thin.

7o within practical limits as otherwise as indicated by the slottedopenings Il' in the cement strip ill of Fig. 2. The openings will beuniformly arranged and preferably staggered throughout the entire areaof the cement strip.

g When the cement strip is used in forming a seam 10 face of the feltcan readily penetrate. This not only tends to prevent the felt at theseam areas from running wet, but greatly facilitates the drying of thefelt in such area when reconditioning the same after prolonged use inaccordance with u the usual practice.

In forming a lapped seam in a drier felt the opposite ends a. and b ofthe felt will be overlapped for a length somewhat greater than the widthof the cement strip I0, all as shown in Fig. 3.

This is because the cement tends to spread when it is softened, and itis obviously desirable that it should not spread beyond the feltextremities. In practice the lower end b of the felt will be placed upona suitable fiat base. A volatile solvent or other softener will then beapplied thereto, em-

ploying about a quart of solvent for each five feet of width of thefelt. The cement strip l0 will then be placed on top of felt end b inthe position as shown in Fig. 3. The upper felt end a so will besimilarly treated with solvent and then be superposed upon the cementstrip l0. A suitable pressure member will then be placed over thelaminated structure. The solvent will soften the cement and cause thesame to flow, entering the fabric'of the felt ends for a distanceadjacent the opposing surfaces thereof. Penetration of the cement intothe fabric will be facilitated by the pressure through the pressuremember, and the opposing surfaces of the felt ends will be forced Thecondition of the seam at the time the felt end a is superposed upon thecement strip isl shown in Fig. 4, and the condition after the cement hassoftened and penetrated into the fabric of the felt ends is representedin Fig. 5. As

the volatile solvent vaporizes 0E the cement sets and hardens, and thefelt will be ready for use in a very short time after the seam isformed.

Because of the tendency of the cement of the strip to spread when it issoftened it is important that the openings formed therein shall be ofsufficiently large size as not to be destroyed under spreading of thecement. While the size of the openings as well as their shape may varyconsiderably, they must have a certain minimum size so that they willprovide permanent openings through the cemented seam at relatively closerecurrent intervals for the purposes above mentioned. Where circularopenings Il are employed as in the strip of Fig. 1 it is preferred tomake them with the diameter of about i0 mm. or larger, making allowancefor the fact that their diameter will decrease to some extent, perhapsas much as 25% or more when the cement softens, even though the cementstrip is itself comparatively It is obvious that the greater the totalarea of theopenings in relation to the bonded area of the fabric, thegreater will be absorptive capacity of the drier -felt at the seam. 0fcourse the total area of the openings should be kept there will beinsufficient bonding to make a strong seam which will withstand thelongitudinal strain on the drier felt during operation.

While the cement strip may be composed solely 5 of cement, it ispreferred to form the same by the use in joining amorbent fabrics. stripI3 after leaving It will be evident to that the present inventionprovides a foolproof 1. A seam forming device the ends of a thickabsorbent fabric drier felt in a cemented strongly bonded lapped seamdevoid 2. A seam forming device the ends of a thick absorbent fabricdrier felt for securing together i action of solvent to spreadlengthwise along the lapped surfaces of the end portions.

' felt cemented seam according to wardly from the of cement and capableof absorbing moisture.

JOHN ROSLUND.

REFERENCES CITED The following references are Iile of this patent:

UNITED STATES PATENTS of record in the Number Name Date 1,383,726Kiracofe July 5, 1921 1,955,083 Muller Apr. 27, 1934 1,970,755 KnollAug. 21, 1934 2,089,469 Dix Aug. 10, 1937 1,038,874 Goodsir, J1' Sept.17, 1912 2,294,088 Kholos Aug. 25, 1942 1,536,533 Sheehan May 5, 1925OTHER REFERENCES Publication .entitled Paper Trade' Journal, pages41,and 42 of November 17, 1932.

